Micrometer-gage



(No Model.)

L. 8., STARRETT. MIGROMETE'R GAGE.

No. 448,089 j Patented Mar. 10, 1891'.

UN rrn STATES LARO-Y S. STARRETT, OF ATHOL, MASSACHUSETTS.

MlCROMETER-GAGE.

SPECIFICATION forming part of Letters Patent No. 448,089, dated March 10, 1891.

Serial No. 309,584. (No model.)

To ctZZ whom it may concern:

Be it known that I, LAROY S. STARRETT, of Athol, in the county of Worcester and Sate of Massachusetts, have invented certain new and useful Improvements in Micrometer-Gages, of which the following, taken in connection with the accompanying drawings, is a specification. The object of this invention is to furnish a speeded micrometer in which the movement of the spindle toward and from the anvil by rotation is much more rapid than in those heretofore known, the instrument being at the same time rendered more sensitive than hitherto. These objects I attain by providing the outer end of the spindle with a milled projecting thumb-piece materially less in diameter than the milled hub at the end of the external sleeve, to which the finger and thumb are usually applied in rotating the spindle. This projecting thumb-piece may be either an integral part of the hub which closes the outer end of the sleeve or a part of the spindle itself prolonged through said hub, or a separate pin or plug extending into it.

Another feature of this invention introduces into the cavity of the threaded barrel a coiled spring surrounding the spindle and serving to keep its screw-threads pressed back into such close engagement with the female screw as to avoid all backlash and insure the utmost accuracy. The screw-thread is preferably ratchet-shaped or with the incline mainly on one side, to present on the other side a square shoulder to the work.

the barrel and a defined shoulder or collar at the end of the threaded part of the spindle.

In the drawings, Figure 1 is a longitudinal section through my improved micrometer with the spindle and anvil in elevation. Fig. 2 is a side view of the instrument complete, and Fig. 3 a perspective view of the threaded spindle with its milled ends. Fig. at is a detail.

A is the anvil, 1 the curved neck, and O the tubular internally-threaded barrel fixed permanently thereto.

D is the spindle,havin g a longitudinal movement toward and from the anvil by a screw engagement within said barrel.

E is the external sleeve revolving outside the barrel and secured to the milled hub F at the outer end of the spindle, so as to move The spring is compressed between the bottom of with it. The sleeve is beveled at its inner end and graduated peripherally in twentyfive equal subdivisions, while the barrel has a straight line of graduations corresponding to its internal threads, preferably in fortieths of an inch. Thus the rotary movement of the sleeve, to the extent of a single oneof its peripheral graduations, will advance the spindle one twenty-fifth part of one-fortieth that is, one-thousandth of an inch.

With the fine threads of these instruments the longitudinal mo ement of the spindle has heretofore been Very slow, since in turning the sleeve by its milled hub F only about half of a complete revolution was gained by each movement of the thumb and finger over said hub. I therefore provide a milled thumbpiece G of greatly-reduced diameter, projecting axially from the end of the hub, either as a part of said hub or of the spindle, or a disti-nct piece inserted therein. finger acting upon this extension G, having a circumference, perhaps, one-third that of the milled part F, will serve to rotate the sleeve and spindle some three times as fast as if the contact were with the larger part, thus savin g much valuable time in adjusting the gage for wide variations in distance. Again, as the leverage upon the spindle is much less in using this extension G, the operator will notice the contact of the gage with the work being measured more readily, thus increasing the sensitiveness 0f the instrument, particularly in gaging delicate or compressible articles. I either form this extension thumbpiece integral with the spindle, of which it then constitutes the extremity, or separate therefrom and made to screw into the operating end of the spindle, as indicated in Fig. 4.

H represents a helical spring surrounding the spindle D and extending from the shoul- The thumb and der J, at the end of its threaded portion, forand nut to cause inaccuracy.

I do not claim, broadly, a spring for avoiding backlash in a micrometer, since in my patent on micrometer-caliper square, No. 399,167, dated March 5, 1889, I have shown a coiled spring around a stationary screwthreaded rod for alike purpose. By my pres ent arrangement the spring, telescoped by the spindle, is concealed and protected by the surrounding sleeve and does not at all come into contact with the screw-threads.

I claim as my invention 1. In a micrometer-gage, the anvil A, the neck B, the fixed tubular barrel 0, threaded internally and having externally a line of longitudinal graduations, and the terminallygraduated sleeve E, revolving outside of said barrel, in combination with the spindle D, having a threaded portion engaging the threaded interior of the barrel, the peripherally-milled end portion F, for turning said sleeve and spindle in adjusting the device, and with the axial extension thumb-piece G, fixed to said spindle D, materially less in diameter than said milled end portion F, for increasing the speed of rotation, substantially as set forth.

2. In a micrometer-gage, the unslotted and internally-threaded barrel 0 and the peripherally-graduated sleeve revolving around it, in combination with the spindle affixed to said sleeve and having a threaded portion engaging within the threaded barrel, and with a spring H, arranged Within the annular space around the unthreaded part of the spindle within said barrel, substantially as set forth.

3. In a micrometer-gage, the anvil A, neck B, and tubular body 0, threaded internally, in combination with the spindle D, having a threaded portion terminating in a defined shoulder J, and with a coiled spring H, telescoped by said spindle and compressed between the shoulder J and the bottom of the cavity in the barrel, substantially as set forth.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, on this 27th day of April, A. D. 1889.

LAROY S. STARRETT.

itnesses:

ANDREW J. HAMILTON, CHAS. A. CANUTH. 

